Internal combustion engines, such as turbocharged diesel engines, include cooling systems to limit temperatures of various engine components. Internal combustion engines are known to be designed with internal cooling passages fir the circulation of coolant to remove thermal energy from the engine components. Additionally, internal combustion engines often utilize turbochargers to increase power by compressing an intake combustion air to a higher density. Such compression results in the heating of the combustion air, which may then be cooled prior to its use via a charge air cooler (or intercooler) to enable the engine to have high volumetric efficiency and low emissions of exhaust pollutants.
It is often desirable to maintain an internal combustion engine and its associated intake combustion air at different temperatures based on engine operation in order to optimize the performance of the engine. Consequently, many internal combustion engines flow a single coolant through a variety of coolers and heat transfer devices in order to alter a temperature of the coolant and ultimately, a temperature of the engine, the inventors herein have recognized potential issues with such systems. As one example, heating and/or cooling a single coolant may not be rapid enough to meet engine intake air temperature demands during engine operation shifts. As a result, engine performance may be decreased and emissions may increase during a length of time needed to heat and/or cool a coolant to a desired coolant temperature that produces a desired intake air temperature of intake air to the engine.
In one example, the issues described above may be addressed by a method for flowing a mixture of coolants, including a first coolant at a first temperature and a second coolant at a second temperature, lower than the first temperature, to a charge air cooler. A temperature of the mixture of coolants is altered via adjusting a ratio of the first coolant to the second coolant in response to an engine operating condition and an outlet temperature of the charge air cooler. In this way, a temperature of intake air delivered to the engine, downstream from the charge air cooler, may be controlled under a variety of engine operating conditions, thereby increasing engine efficiency.
As one example, only a first coolant at a higher, first temperature may be used during a first mode in order to increase a temperature of one or more of an engine, a CAC, and an intake air temperature. Further, only a second coolant at a lower, second temperature may be used during a second mode in order to decrease a temperature of one or more of the engine, the CAC, and the intake air temperature. A combination of the first (e.g., hotter) coolant and the second (e.g., cooler) coolant may be used to either increase or decrease one or more of the engine temperature, the CAC temperature, and the engine intake air temperature based on a ratio of the hotter to cooler coolant. In this way, the CAC temperature, the engine temperature, and/or the intake air temperature may be gradually changed or more dramatically changed based on operation in either the third mode or the first/second modes, respectively.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.